In message , Jeff Layman
writes
There are special products (based on gypsum) which break up clay, but
these are not cheap for a reasonably large area and after a while the
clay gets claggy again. They also make the soil alkaline.

The benefit of gypsum (as opposed to much cheaper lime) is that it does
not change the pH of the soil.
--
hugh
It may be more complicated but is it better?